Monomer Design Enables Mechanistic Mapping of Anionic Ring‐Opening Polymerization of Aromatic Thionolactones

Abstract Degradable chalcogenide polyesters, e.g., polythioesters (PTEs), typically exhibit improved thermal, mechanical, and optical properties. Anionic ring‐opening polymerization (ROP) of thionolactones, an intrinsically promising yet underexplored approach to accessing PTEs, however, is still limited by: intolerance of metal catalysts, inadequate control over chain growth, and the absence of aromatic system. Monomer design‐boosted mechanistic studies may address the above challenges. Here, we present a new and highly reactive thionolactone synthesized from 1,1′‐binaphthyl‐2,2′‐diol (BINOL). Our investigations into polymerization kinetics and thermodynamics have underscored the importance of rapid initiation, eventually leading to the discovery of tetrabutylammonium 2‐naphthyl‐thiocarboxylate as a distinctive initiator that enables genuinely controlled and living polymerization of thionolactones. Ultimately, the atropisomerism inherent in BINOL has resulted in the creation of axially chiral PTE materials with tailored molecular weights, enantiomeric compositions, and topologies.